Residential and commercial buildings require heat, hot water, and electrical power. Typically, a furnace or boiler which burns fuel, e.g., oil, natural gas, or propane, will generally provide all of the heating needs in the residential or commercial building. A furnace generally consists of two basic components, a combustion chamber where the fuel is burned, and a heat exchanger where the hot combustion gases transfer heat to a distribution medium, e.g., water, steam, or air. In addition, the furnace, or a separate hot water heater may provide the hot water needs of the residential or commercial building.
Generally, a large, centralized power generation facility provides the electrical power needs of a residential or commercial building.
A fuel cell power system is also capable of providing electrical power. A fuel cell power system generally includes a fuel processor, a fuel cell assembly or stack, and a power conditioner. The fuel processor converts fuel, e.g., natural gas or propane, into a hydrogen-rich gas. The fuel processor generally includes a reformer for processing the fuel into a hydrogen-rich gas or reformate. For fuel cells having a Proton Exchange Membrane, desirably the fuel processor includes a carbon monoxide (CO) cleanup device which reduces the CO content of the reformate.
The fuel cell assembly or stack electrochemically converts hydrogen in the reformate, and oxygen in the oxidant, e.g., air, directly into DC electricity. The power conditioner converts the DC produced by the fuel cell stack to a more useful 120 or 220 VAC.
Attempts have been made for integrating a boiler or furnace with a fuel cell assembly for generating heat and electrical power. For example, U.S. Pat. No. 5,401,589 to Palmer et al. discloses the application of a fuel cell stack to a power generation system in which the waste heat of the system is utilized. For example, heat produced in a fuel cell stack may be used in a reformer or may be used for space heating. In addition, exhaust from a burner of a fuel processor may be connected to a turbine and a small generator to supplement the electrical power output from a fuel cell stack, or coupled with a heat exchanger to provide either process heating or space heating.
U.S. Pat. No. 5,335,628 to Dunbar discloses an integrated boiler/fuel cell system having a water recirculation loop that serves the dual purpose of acting as a cooling agent for a fuel cell and acting as a heat and/or water source for a boiler. Heat from the boiler may be used an energy source to reform natural gas for use in the fuel cell.
U.S. Pat. No. 5,432,710 to Ishimaru et al. discloses an energy supply system having a fuel cell, a reformer for providing a supply of reformate to the fuel cell, a separate boiler, and control means for optimizing energy costs, energy consumption, and emission of pollutants.
The above-noted prior art systems are limited in their integration of the boiler/furnace with a fuel cell power system by operating a reformer to optimize the production of hydrogen-rich reformate and in which the reformate from the reformer is directed solely to a fuel cell assembly.
Therefore, there exists a need for compact integrated systems having a fuel processor, a furnace, and a fuel cell assembly which overcome the limitations of the prior art for efficiently providing heat, hot water, and/or electrical power to a building.